powerpc: Add ppc64 hard lockup detector support (c54b2bf1) · Commits · 戴 / test

The hard lockup detector uses a PMU event as a periodic NMI to detect if we are stuck (where stuck means no timer interrupts have occurred). Ben's rework of the ppc64 soft disable code has made ppc64 PMU exceptions a partial NMI. They can get disabled if an external interrupt comes in, but otherwise PMU interrupts will fire in interrupt disabled regions. We disable the hard lockup detector by default for a few reasons: - It breaks userspace event based branches on POWER8. - It is likely to produce false positives on KVM guests. - Since PMCs can only count to 2^31, counting cycles means we might take multiple PMU exceptions per second per hardware thread even if our hard lockup timeout is 10 seconds. It can be enabled via a boot option, or via procfs. Signed-off-by:

Anton Blanchard <anton@samba.org> Signed-off-by:

Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/Kconfig

+1 −0

Original line number	Diff line number	Diff line
		@@ -152,6 +152,7 @@ config PPC
		select DCACHE_WORD_ACCESS if PPC64 && CPU_LITTLE_ENDIAN
		select NO_BOOTMEM
		select HAVE_GENERIC_RCU_GUP
		select HAVE_PERF_EVENTS_NMI if PPC64

		config GENERIC_CSUM
		def_bool CPU_LITTLE_ENDIAN

arch/powerpc/include/asm/nmi.h

0 → 100644

+4 −0

Original line number	Diff line number	Diff line
		#ifndef _ASM_NMI_H
		#define _ASM_NMI_H

		#endif /* _ASM_NMI_H */

arch/powerpc/kernel/setup_64.c

+20 −0

Original line number	Diff line number	Diff line
		@@ -37,6 +37,7 @@
		#include <linux/memblock.h>
		#include <linux/hugetlb.h>
		#include <linux/memory.h>
		#include <linux/nmi.h>

		#include <asm/io.h>
		#include <asm/kdump.h>
		@@ -779,3 +780,22 @@ unsigned long memory_block_size_bytes(void)
		struct ppc_pci_io ppc_pci_io;
		EXPORT_SYMBOL(ppc_pci_io);
		#endif

		#ifdef CONFIG_HARDLOCKUP_DETECTOR
		u64 hw_nmi_get_sample_period(int watchdog_thresh)
		{
		return ppc_proc_freq * watchdog_thresh;
		}

		/*
		* The hardlockup detector breaks PMU event based branches and is likely
		* to get false positives in KVM guests, so disable it by default.
		*/
		static int __init disable_hardlockup_detector(void)
		{
		watchdog_enable_hardlockup_detector(false);

		return 0;
		}
		early_initcall(disable_hardlockup_detector);
		#endif

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